EP4642272A1

EP4642272A1 - An adaptable aerosol-generating system and method

Info

Publication number: EP4642272A1
Application number: EP23837374.0A
Authority: EP
Inventors: Stéphane Bilat; Gregory André CRISTIAN
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2022-12-28
Filing date: 2023-12-27
Publication date: 2025-11-05
Also published as: WO2024141545A1; JP2026502163A; CN120390595A; KR20250128356A

Abstract

There is provided an aerosol-generating system. The aerosol-generating system comprises a heating element for heating an aerosol-forming substrate The aerosol-generating system further comprises a power supply for supplying power to the heating element. The aerosol-generating system further comprises a controller. The controller is configured to, in a first mode, control the power to the heating element from the power supply. The controller is further configured to, in a first mode measure or determine a baseline resistance of the heating element. The controller is further configured to, in a first mode, measure the resistance of the heating element during a session of one or more puffs. The controller is further configured to, in a first mode, compare the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance. The controller is further configured to, in a first mode, determine an adverse condition when the resistance exceeds the baseline resistance by a first quantity. In the first mode the controller is configured to continually adjust the first quantity during the session dependent on one or more parameters measured or determined by the controller.

Description

AN ADAPTABLE AEROSOL-GENERATING SYSTEM AND METHOD

The present disclosure relates to an adaptable aerosol-generating system and an adaptable method of operation for the aerosol-generating system.

Many aerosol-generating systems comprise a liquid storage portion for storing liquid aerosol-forming substrate, and an electric heater for heating the liquid aerosol-forming substrate. These aerosol-generating systems sometimes comprise electric circuitry configured to determine the level of liquid aerosol-forming substrate remaining in the liquid storage portion, or if the liquid storage portion is depleted of liquid aerosol-forming substrate. In particular, it is beneficial to avoid the liquid aerosol-forming substrate depleting to a level such that insufficient liquid is supplied to the electric heater. If insufficient liquid is supplied to the electric heater and the electric heater is powered, the electric heater may reach a temperature above its intended operational temperature. This is because there is less liquid aerosol-forming substrate available for the electric heater to vaporise. Excess heat may result in excess carbonyl production from the liquid aerosol-forming substrate which remains at the heating element, and the delivery of an undesirable burnt aerosol taste to a user.

WO2018019533A1 discloses a method of determining such an adverse condition. An initial electrical resistance of the electric heater is measured and a subsequent electrical resistance of the electrical heater is measured. When the difference between the initial electrical resistance and the subsequent electrical resistance is greater than a maximum threshold value or is less than a minimum threshold value, the adverse condition is detected. However, users may use these aerosol-generating systems in many different ways. For example, some users may take many short puffs in quick succession, whereas other users may take longer puff with long breaks in between. The aerosol-generating system may therefore adapt certain parameters depending on how the aerosol-generating system is used by the user, to ensure consistent aerosol generation. The variation in parameters associated with how the user uses the aerosol-generating system, may affect the ability of previous methods to detect such adverse conditions with speed and accuracy. Therefore, it would be beneficial to provide an aerosol-generating system and method for determining an adverse condition which is adaptable dependent on the usage characteristics of the aerosol-generating system, in order to detect adverse conditions faster and with more accuracy.

According to the present disclosure, there is provided an aerosol-generating system. The aerosol-generating system comprises a heating element for heating an aerosol-forming substrate The aerosol-generating system further comprises a power supply for supplying power to the heating element. The aerosol-generating system further comprises a controller. The controller is configured to, in a first mode, control the power to the heating element from the power supply. The controller may be further configured to, in the first mode measure or determine a baseline resistance of the heating element. The controller may be further configured to, in the first mode, measure the resistance of the heating element during a session of one or more puffs. The controller may be further configured to, in the first mode, compare the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance. The controller may be further configured to, in the first mode, determine an adverse condition when the resistance exceeds the baseline resistance by a first quantity. In the first mode the controller may be configured to continually adjust the first quantity during the session dependent on one or more parameters measured or determined by the controller.

Advantageously, the aerosol-generating system according to the present disclosure may therefore adapt to exactly how the aerosol-generating system is used by the user. When varying the first quantity dependent on one or more parameters measured or determined by the controller, the aerosol-generating system may detect adverse conditions faster and with more accuracy than previous aerosol-generating systems known in the art. As a result, the risk of a burnt taste and carbonyl generation from a dry heating element may be minimized.

Measuring the resistance of the heating element may comprise measuring or determining one or more characteristic quantities of the heating element, and calculating the resistance of the heating element based on the one or more characteristic quantities of the heating element. For example, the one or more characteristic quantities may comprise one or more of the voltage across the heating element, the current through the heating element, and the conductance of the heating element.

The heating element may form part of a heating element circuit. Measuring the resistance of the heating element may comprise measuring or determining one or more characteristic quantities of the heating element circuit, and calculating the resistance of the heating element based on the one or more characteristic quantities of the heating element circuit. For example, the other characteristic quantity may comprise one or more of the voltage across the heating element, a voltage across another component of the heating element circuit, the current through the heating element, a current through another component of the heating element circuit, the conductance of the heating element, a conductance of another component of the heating element circuit, and a resistance of another component of the heating element circuit. The other component of the heating element circuit may be in series with the heating element. The other component of the heating element circuit may be a resistor.

The controller may be further configured to, in the first mode measure or determine a baseline characteristic quantity of the heating element. The controller may be further configured to, in the first mode, measure a characteristic quantity of the heating element during a session of one or more puffs. The controller may be further configured to, in the first mode, compare the characteristic quantity of the heating element to the baseline characteristic quantity or to a threshold based on the baseline characteristic quantity. The controller may be further configured to, in the first mode, determine an adverse condition when the characteristic quantity exceeds the baseline characteristic quantity by a first quantity. In the first mode the controller may be configured to continually adjust the first quantity during the session dependent on one or more parameters measured or determined by the controller.

The characteristic quantity may be the resistance of the heating element. The characteristic quantity may be the voltage across the heating element. The characteristic quantity may be the current through the heating element. The characteristic quantity may be the conductance of the heating element. If the characteristic quantity is the conductance of the heating element, the controller may be further configured to, in the first mode, determine an adverse condition when a baseline conductance exceeds the conductance by a first quantity.

The controller may be further configured to, in the first mode measure or determine a baseline characteristic quantity of the heating element circuit. The controller may be further configured to, in the first mode, measure a characteristic quantity of the heating element circuit during a session of one or more puffs. The controller may be further configured to, in the first mode, compare the characteristic quantity of the heating element circuit to the baseline characteristic quantity or to a threshold based on the baseline characteristic quantity. The controller may be further configured to, in the first mode, determine an adverse condition when the characteristic quantity exceeds the baseline characteristic quantity by a first quantity. In the first mode the controller may be configured to continually adjust the first quantity during the session dependent on one or more parameters measured or determined by the controller.

The characteristic quantity of the heating element circuit may be the voltage across a component in series with the heating element. The characteristic quantity of the heating element circuit may be a ratio or proportion of voltages across the component in series with the heating element, and the heating element. The characteristic quantity of the heating element circuit may be the current through the component in series with the heating element. The characteristic quantity of the heating element circuit may be a ratio or proportion of currents through the component in series with the heating element, and the heating element. The characteristic quantity of the heating element circuit may be the conductance of the component in series with the heating element. The characteristic quantity of the heating element circuit may be a ratio or proportion of conductances of the component in series with the heating element, and the heating element. The component in series with the heating element may be a resistor.

The aerosol-generating system may be configured to display a warning to a user when the controller determines an adverse condition during one or more puffs. The aerosol-generating system may be configured to display a warning to a user when the controller determines an adverse condition during one puff. The aerosol-generating system may be configured to display a warning to a user when the controller determines an adverse condition during a plurality of puffs. Advantageously, the user may therefore be alerted of the adverse condition and adjust their behaviour accordingly, for example by not puffing on the aerosol-generating system, by refilling or replacing the aerosol-forming substrate, or replacing a cartridge.

The controller may be configured to stop or reduce power supplied to the heating element when the controller determines an adverse condition during one or more puffs. Preferably, the controller may be configured to stop or reduce power supplied to the heating element such that no aerosol may be produced at the aerosol-generating system when the controller determines an adverse condition during one or more puffs. Advantageously, the user may therefore not be able to generate aerosol using the aerosol-generating system, and so would not be exposed to the risk of a burnt taste and carbonyl generation from a dry heating element.

The controller may be configured to measure the resistance of the heating element at regular time intervals during the session of one or more puffs. The controller may be configured to measure the resistance of the heating element at regular time intervals during each puff of the session of one or more puffs. Advantageously, the controller may therefore rapidly detect an adverse condition if an adverse condition were to be present half way through a puff.

The controller may be configured to compare the resistance of the heating element to the baseline resistance or a threshold based on the baseline resistance at regular time intervals during the session of one or more puffs. The controller may be configured to compare the resistance of the heating element to the baseline resistance or a threshold based on the baseline resistance at regular time intervals during each puff the session of one or more puffs. Advantageously, the controller may therefore rapidly detect an adverse condition if an adverse condition were to be present half way through a puff.

The duration of the regular time intervals may be between 10 microseconds and 250 milliseconds. Preferably, the duration of the regular time intervals is between 0.1 milliseconds and 100 milliseconds, more preferably, the duration of the regular time intervals is between 1 millisecond and 20 milliseconds, more preferably still, the duration of the regular time intervals is between 1 millisecond and 10 milliseconds, more preferably still, the duration of the regular time intervals is substantially equal to 3 milliseconds.

The controller may be configured to adjust the first quantity dependent on the power supplied to the heating element. The controller may be configured to adjust the first quantity during each of the one or more puffs dependent on the power supplied to the heating element. The resistance of the heating element is dependent on the temperature of the heating element. If more power is supplied to the heating element, the temperature of the heating element will increase, and the resistance of the heating element will increase. Therefore, it is advantageous to adjust the first quantity dependent on the power supplied to the heating element, as more accurate detection of adverse conditions will be achieved.

The aerosol-generating system may further comprise an air inlet and an air outlet. The aerosol-generating system may further comprise an air flow passage extending between the air inlet and the air outlet. The aerosol-generating system may further comprise a sensor assembly in communication with the air flow passage. The sensor assembly may be configured to measure a pressure or a flow rate within the airflow passage. The controller may be configured to adjust the first quantity during each of the one or more puffs dependent on the pressure or the flow rate measured by the sensor assembly. The resistance of the heating element is dependent on the temperature of the heating element. If a greater flow rate is present in the airflow passage, and assuming the same power is supplied to the heating element, the temperature of the heating element will decrease. As a result, the resistance of the heating element will decrease. Therefore, it is advantageous to adjust the first quantity dependent on the pressure or the flow rate within the airflow passage, as more accurate detection of adverse conditions will be achieved.

The controller may be configured to detect a start of a puff when a user puffs on the aerosol-generating system based on the pressure or the flow rate measured by the sensor assembly. The controller may be configured to adjust the first quantity dependent on the total number of puffs elapsed during the session. The controller may be configured to adjust the first quantity dependent on a total time elapsed since the start of the session. During a session, other components of the aerosol-generating system which surround the heating element will increase in temperature. As a result, as a session progresses less heat is lost from the heating element to the other components of the aerosol-generating system which surround the heating element. Therefore, the resistance of the heating element will increase as a session progresses. Therefore, it is advantageous to adjust the first quantity dependent on the total number of puffs elapsed during the session or the total time elapsed since the start of the session, as more accurate detection of adverse conditions will be achieved.

The controller may be configured to adjust the first quantity during each of the one or more puffs dependent on a puff time elapsed since the start of each of the one or more puffs. The controller may be configured to linearly increase the first quantity during each of the one or more puffs dependent on a puff time elapsed since the start of each of the one or more puffs. During each puff, other components of the aerosol-generating system which surround the heating element will increase in temperature. As a result, as each puff progresses less heat is lost from the heating element to the other components of the aerosol-generating system which surround the heating element. Therefore, the resistance of the heating element will increase as each puff progresses. Therefore, it is advantageous to adjust the first quantity during each of the one or more puffs dependent on a puff time elapsed since the start of each of the one or more puffs, as more accurate detection of adverse conditions will be achieved.

The controller may configured to adjust the first quantity dependent on a time elapsed since an end of a preceding puff in the session.

The controller may be configured to calculate a scaled quantity following the end of each puff in the session. The scaled quantity may be dependent on a maximum value of the first quantity during a preceding puff in the session. The controller may be configured to adjust the scaled quantity dependent on a time elapsed since an end of the preceding puff. The controller may be configured to successively reduce the scaled quantity from the maximum value during the preceding puff at regular time intervals following the end of the preceding puff. The controller may be configured to successively reduce the scaled quantity from the maximum value at regular time intervals following the end of preceding puff by a pre-determined proportion of the maximum value. The controller may be configured to adjust the first quantity such that the first quantity is equal to the scaled quantity following the end of the preceding puff in the session and before the start of an ensuing puff in the session.

The controller may be configured to calculate or determine a first quantity value during each ensuing puff. The controller may be further configured to adjust the first quantity during each ensuing puff in the session such that the first quantity is equal to the scaled quantity until the first quantity value exceeds the scaled quantity. The controller may be further configured to adjust the first quantity during each ensuing puff in the session such that the first quantity is equal to the first quantity value if the first quantity value exceeds the scaled quantity at the start of the ensuing puff. The controller may be further configured to adjust the first quantity during each ensuing puff in the session such that the first quantity is equal to the scaled quantity unless the first quantity value exceeds the scaled quantity. The controller may be configured to, once the first quantity value exceeds the scaled quantity during the ensuing puff in the session, adjust the first quantity during the ensuing puff such that the first quantity is equal to the first quantity value. The controller may be configured to, once the first quantity value exceeds the scaled quantity during the ensuing puff in the session, adjust the first quantity during the ensuing puff such that the first quantity is equal to the first quantity value for the remainder of the ensuing puff. The controller may be configured to, once the first quantity value exceeds the scaled quantity during the ensuing puff in the session, adjust the first quantity during the ensuing puff dependent on one or more parameters measured or determined by the controller, as disclosed above. Advantageously, this ensures that the more sensitive of thresholds is used to identify whether an adverse condition is present.

The controller may be configured to calculate or determine the first quantity value during each ensuing puff dependent on the same parameters used to calculate or determine the first quantity during a first puff. That is, the controller may be configured to calculate or determine the first quantity value during each ensuing puff dependent on the power supplied to the heating element. The controller may be configured to calculate or determine the first quantity value during each ensuing puff dependent on the pressure or the flow rate measured by the sensor assembly. The controller may be configured to calculate or determine the first quantity value during each ensuing puff dependent on the total number of puffs elapsed during the session. The controller may be configured to calculate or determine the first quantity value during each ensuing puff dependent on a total time elapsed since the start of the session. The controller may be configured to calculate or determine the first quantity value during each ensuing puff dependent on a puff time elapsed since the start of each ensuing puff. The controller may be configured to linearly increase the first quantity value during each ensuing puff dependent on a puff time elapsed since the start of each ensuing puff. The controller may be configured to calculate or determine the first quantity value during each ensuing puff dependent on a time elapsed since an end of the preceding puff in the session.

The controller may be configured to adjust the first quantity dependent on an ambient temperature. The resistance of the heating element is dependent on the temperature of the heating element. If the ambient temperature of the environment in which the aerosol-generating system is located increases, the temperature of the heating element will also increase, as heat is lost less quickly when the heating element is heated. The resistance of the heating element will therefore increase. Therefore, it is advantageous to adjust the first quantity dependent on the ambient temperature as more accurate detection of adverse conditions may be achieved. The baseline resistance may be adjusted as a function of ambient temperature before proceeding to determine an adverse condition.

The aerosol-generating system may comprise an aerosol-generating device and a cartridge. The cartridge may be couplable to the aerosol-generating device. The aerosolgenerating device may comprise the controller and the power supply. The cartridge may comprise the heating element. The controller may be configured to determine a classification of the cartridge when the cartridge is coupled to the aerosol-generating device. The controller may be configured to adjust the first quantity dependent on the classification of the cartridge. Advantageously, the characteristics of the cartridge may vary dependent on the classification of the cartridge. For example, cartridges may have different heating elements which, display different increases in resistance with temperature. Therefore, it is advantageous to adjust the first quantity dependent on the classification of the cartridge, as more accurate detection of adverse conditions may be achieved.

The controller may be configured to determine the baseline resistance of the heating element after the user couples the cartridge to the aerosol-generating device. The controller may be configured to determine the baseline resistance of the heating element after one or both of the user switching the aerosol-generating system on, or the user not puffing on the device for a pre-determined cooldown time period. Advantageously, the baseline resistance of the heating element is therefore determined when the heater is sufficiently cool.

The first quantity may be a first resistance equal to a proportion of the baseline resistance. Advantageously, an accurate detection of adverse conditions may be achieved regardless of the initial baseline resistance of the heating element.

The controller may be configured to continually adjust the first quantity at regular time intervals during the session. The controller may be configured to continually adjust the first quantity at regular time intervals during each of the puffs of the session The session of one or more puffs may be a session of a plurality of puffs.

The heating element may be a resistive heating element. The resistive heating element may take the form of a mesh, array or fabric of electrically conductive filaments. Preferably, the heating element comprises a mesh. The electrically conductive filaments may define interstices between the filaments and the interstices may have a width of between 10 micrometres and 100 micrometres. The electrically conductive filaments may form a mesh of size between 160 and 600 Mesh US (+/- 10%) (i.e. between 160 and 600 filaments per inch (+/- 10%)). The width of the interstices is preferably between 75 micrometres and 25 micrometres. The percentage of open area of the mesh, which is the ratio of the area of the interstices to the total area of the mesh is preferably between 25 and 56%. The mesh may be formed using different types of weave or lattice structures. Alternatively, the electrically conductive filaments consist of an array of filaments arranged parallel to one another. The electrically conductive filaments may have a diameter of between 10 micrometres and 100 micrometres, preferably between 8 micrometres and 50 micrometres, and more preferably between 8 micrometres and 39 micrometres. The filaments may have a round cross section or may have a flattened cross-section. The area of the mesh may be small, preferably less than or equal to 25 mm2 , allowing it to be incorporated in to a handheld system. The mesh, array or fabric of electrically conductive filaments may, for example, be rectangular and have dimensions of 5 mm by 2 mm. Preferably, the mesh or array of electrically conductive filaments covers an area of between 10% and 50% of the area of the heater assembly. More preferably, the mesh or array of electrically conductive filaments covers an area of between 15 and 25% of the area of the heater assembly. The filaments may be formed by etching a sheet material, such as a foil. This may be particularly advantageous when the heater assembly comprises an array of parallel filaments. If the heating element comprises a mesh or fabric of filaments, the filaments may be individually formed and knitted together.

The resistive heating element may comprise an etched heater element. For example, a resistive heater element etched into a sheet or other form of conductive material. The resistive heating element may comprise a stamped heater. For example, a resistive heater element stamped out from a sheet or other form of conductive material. The resistive heating element may comprise a coils heater. For example, a single filament or strip of conductive material formed in a coil shape. The resistive heating element may comprise a ceramic heater. For example, the resistive heating element may comprise conductive tracks on porous ceramic. The conductive tracks may be formed from a conductive material.

Preferred materials for the resistive heating element are 304, 316, 304L, and 316L stainless steel.

The aerosol-forming substrate may be a liquid or gel aerosol-forming substrate.

When the controller determines an adverse condition during one or more puffs, the controller may be configured to switch from the first mode to a second mode. In, the second mode the controller may be configured to confirm an adverse condition when the resistance exceeds the baseline resistance by a second quantity. Advantageously, this second mode feature may allow the controller to determine whether there really is an adverse condition, or if an erroneous reading gave a false-positive result that an adverse condition is present.

The second quantity may be a pre-determined quantity. The second quantity may be a second resistance equal to a proportion of the baseline resistance. The second quantity may be a second resistance equal to a proportion of the first resistance. The second quantity may be different from the first quantity. In the second mode the controller may be configured to control the power supplied to the heating element from the power supply. In the second mode, the power supplied to the heating element from the power supply may be constant for the duration of each puff of the session. In the second mode, the power supplied to the heating element from the power supply during each puff of the session may be insufficient for generating aerosol from the aerosolforming substrate. Advantageously, this feature may prevent the heating element from being overheated when an adverse condition is present at the heating element, such as insufficient liquid supplied to the heating element. In the second mode the controller may be configured to switch to the first mode if an adverse condition is not confirmed by the controller within N puffs of the controller switching to the second mode, wherein N is an integer number of puffs. N may be an integer greater than or equal to 1 , and may be less than or equal to 10. Preferably, N is an integer greater than or equal to 2, and may be less than or equal to 10. Advantageously, this prevents the controller switching back to the first mode when a reading gave a false-negative result that an adverse condition is not present. The controller may be configured detect a change of cartridge, and configured to switch from the second mode to the first mode if a change of cartridge is detected. When the controller determines an adverse condition during M puffs, the controller may be configured to switch from the first mode to a second mode. M may be an integer greater than or equal to 2, and may be less than or equal to 10. Advantageously, this feature may prevent the controller from switching to the second mode if only one erroneous reading gave a false-positive result that an adverse condition is present.

The controller may comprise a computer readable memory. The computer readable memory may store a look-up table comprising a plurality of power profiles and a plurality of ranges of pressure or the flow rate. Each of the ranges of the pressure or the flow rate may correspond to at least one of the power profiles. The pressure ranges or the flow rate ranges may be of substantially equal magnitude. Alternatively, the pressure ranges or the flow rate ranges may be of different magnitudes. This may mean that the pressure ranges or the flow rate ranges are better suited to typical variations in pressure during a puff. The number of pressure ranges or the flow rate ranges in the look-up table may be between 2 and 1000, preferably between 2 and 100, more preferably between 2 and 50, more preferably still between 2 and 20, more preferably still between 2 and 15, more preferably still between 4 and 10, and most preferably between 7 and 9. The controller may be further configured in the first mode to select a power profile from the plurality of power profiles to control the supply of power to the heating element during a puff, the selection dependent on the pressure or the flow rate measured by the sensor assembly. Advantageously, this feature may minimise the amount of calculation required of the controller, reducing the computing power necessary.

The look-up table may further comprise a plurality of system profiles. Each of the power profiles may correspond to one of the ranges of the pressure or the flow rate and one of the system profiles. The controller may be configured in the first mode to select a power profile from the plurality of power profiles to control the supply of power to the heating element during a puff, the selection dependent on the pressure or the flow rate measured by the sensor assembly and a system profile selected by a user. Advantageously, this allows the user to control, at least in part, the desired characteristics of the aerosol generation.

Each power profile may comprise a plurality of power values. Each of the plurality of power values may correspond to a range of time since the start of a puff. The time ranges may be of equal length. The time ranges may be between 0 milliseconds and 2000 milliseconds. Preferably, the lengths of the time ranges may be between 10 milliseconds and 1800 milliseconds. More preferably, the lengths of the time ranges may be between 50 milliseconds and 1500 milliseconds. More preferably still, the lengths of the time ranges may be between 200 milliseconds and 1200 milliseconds. More preferably still, the lengths of the time ranges may be between 600 milliseconds and 1200 milliseconds. The time ranges may be of different lengths. This may mean that the time ranges are best suited to typical variations in pressure during a puff. The number of time ranges in the look-up table may be between 2 and 1000. Preferably, the number of time ranges in the look-up table is between 2 and 100, more preferably between 2 and 50, even more preferably between 2 and 20. More preferably still, the number of time ranges in the look-up table is between 2 and 10, more preferably between 4 and 8, and even more preferably between 5 and 7. The controller may be configured in the first mode to control the supply of power to the heating element during a puff dependent on the plurality of power values and the time since the start of the puff.

Each power profile may further comprise a plurality of first quantity values. Each of the plurality of first quantity values may correspond to one of the plurality of power values. The controller may be configured to adjust the first quantity dependent on a selected first quantity value from the first quantity values stored in the look-up table. Advantageously, this feature may eliminate the need for the controller to calculate the first quantity, significantly reducing the computing power necessary. The controller may be configured to adjust the first quantity to be equal to the selected first quantity value. The first quantity values may be proportions of the baseline resistance. The controller may be configured to determine a first resistance value from a product of the selected first quantity value and the baseline resistance. The controller may be configured to adjust the first quantity to be equal to the first resistance value.

Each power profile may further comprise a plurality of first maximum resistance values. Each of the plurality of first maximum resistance values may correspond to one of the plurality of power values and to one of the plurality of first quantity values. The controller may be configured to adjust the first quantity dependent on both the selected first quantity value and a selected first maximum resistance value from the plurality of first maximum resistance values. The controller may be configured to adjust the first quantity to be equal to the lower of the first resistance value and the selected first maximum resistance value. Advantageously, this may prevent the first quantity being too high, and hence the controller not being sufficiently sensitive to adverse conditions, in the event that the baseline resistance is particularly high.

According to the present disclosure, there is further provided a method of determining an adverse condition in an aerosol-generating system. The aerosol-generating system may comprise a heating element for heating an aerosol-forming substrate. The aerosol-generating system may comprise a power supply for supplying power to the heating element. The aerosol-generating system may comprise a controller. The method may comprise the step of, in a first mode, controlling the power to the heating element from the power supply. The method may comprise the step of measuring or determining a baseline resistance of the heating element. The method may comprise the step of measuring the resistance of the heating element during a session of one or more puffs. The method may comprise the step of comparing the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance. The method may comprise the step of determining an adverse condition when the resistance exceeds the baseline resistance by a first quantity. The method may comprise the step of continually adjusting the first quantity during the session dependent on one or more parameters measured or determined by the controller.

Advantageously, the method of determining an adverse condition in an aerosol-generating system according to the present disclosure may therefore adapt to exactly how the aerosolgenerating system is used by the user. When varying the first quantity dependent on one or more parameters measured or determined by the controller, the method may detect adverse conditions faster and with more accuracy than previous method known in the art. As a result, the risk of a burnt taste and carbonyl generation from a dry heating element may be minimized.

Continually adjusting the first quantity during the session dependent on one or more parameters may comprise continually adjusting the first quantity during each puff of the session dependent on one or more parameters.

The method may further comprise the step of displaying a warning to a user when the controller determines an adverse condition during one or more puffs. The method may further comprise the step of displaying a warning to a user when the controller determines an adverse condition during one puff. The method may further comprise the step of displaying a warning to a user when the controller determines an adverse condition during a plurality of puffs. Advantageously, the user may therefore be alerted of the adverse condition and adjust their behaviour accordingly, for example by not puffing on the aerosol-generating system, by refilling or replacing the aerosol-forming substrate, or replacing a cartridge.

The method may further comprise the step of stopping or reducing power supplied to the heating element when the controller determines an adverse condition during one or more puffs. The method may further comprise the step of stopping or reducing power supplied to the heating element when the controller determines an adverse condition during one puff. The method may further comprise the step of stopping or reducing power supplied to the heating element when the controller determines an adverse condition during a plurality of puffs. Advantageously, the user may therefore be unable to generate aerosol using the aerosol-generating system, and so would not be exposed to the risk of a burnt taste and carbonyl generation from a dry heating element.

Measuring the resistance of the heating element during a session of one or more puffs may comprise measuring the resistance of the heating element at regular time intervals during the session of one or more puffs. Measuring the resistance of the heating element during a session of one or more puffs may comprise measuring the resistance of the heating element at regular time intervals during each puff of the session of one or more puffs. Advantageously, the method may therefore rapidly detect an adverse condition if an adverse condition were to be present half way through a puff.

Comparing the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance may comprise comparing the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance at regular time intervals during the session of one or more puffs. Comparing the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance may comprise comparing the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance at regular time intervals during each puff of the session of one or more puffs. Advantageously, the method may therefore rapidly detect an adverse condition if an adverse condition were to be present half way through a puff.

The one or more parameters may comprise the power supplied to the heating element. Advantageously, for reasons given above, a more accurate detection of adverse conditions may therefore be achieved.

The aerosol-generating system may further comprise an air inlet and an air outlet; and an air flow passage extending between the air inlet and the air outlet. The aerosol-generating system may further comprise a sensor assembly in communication with the air flow passage, the sensor assembly being configured to measure a pressure or a flow rate within the airflow passage. The controller may be configured to detect the start of a puff when a user puffs on the aerosolgenerating system based on the pressure or the flow rate measured by the sensor assembly. The one or more parameters may comprise the pressure or the flow rate measured by the sensor assembly. The resistance of the heating element is dependent on the temperature of the heating element. If a greater flow rate is present in the airflow passage, and assuming the same power is supplied to the heating element, the temperature of the heating element will decrease. As a result, the resistance of the heating element will decrease. Therefore, it is advantageous to adjust the first quantity dependent on the pressure or the flow rate within the airflow passage as more accurate detection of adverse conditions may be achieved.

The one or more parameters may comprise a total number of puffs elapsed during the session. During a session, other components of the aerosol-generating system which surround the heating element will increase in temperature. As a result, as a session progresses less heat is lost from the heating element to the other components of the aerosol-generating system which surround the heating element. Therefore, the resistance of the heating element will increase as a session progresses. Therefore, it is advantageous to adjust the first quantity dependent on the total number of puffs elapsed during the session or the total time elapsed since the start of the session, as more accurate detection of adverse conditions may be achieved.

The one or more parameters may comprise a total time elapsed since the start of the session. The one or more parameters may comprise a puff time elapsed since the start of each of the one or more puffs. Continually adjusting the first quantity during the session dependent on the puff time elapsed since the start of each of the one or more puffs may comprise linearly increasing the first quantity during each of the one or more puffs dependent on a puff time elapsed since the start of each of the one or more puffs. During each puff, other components of the aerosol-generating system which surround the heating element will increase in temperature. As a result, as each puff progresses less heat is lost from the heating element to the other components of the aerosol-generating system which surround the heating element. Therefore, the resistance of the heating element will increase as each puff progresses. Therefore, it is advantageous to adjust the first quantity during each of the one or more puffs dependent on a puff time elapsed since the start of each of the one or more puffs, as more accurate detection of adverse conditions may be achieved.

The one or more parameters may comprise a time elapsed since an end of a preceding puff in the session. Following a puff, the heating element and the surrounding components begin to cool, and the temperature of the heating element is reduced. The resistance of the heating element is also therefore reduced, and a lower resistance threshold at which an adverse condition may be detected will be necessary to accurately detect the adverse condition. Advantageously therefore, adjusting the first quantity during each of the one or more puffs dependent on the time elapsed since an end of a preceding puff in the session allows for more accurate detection of adverse conditions. The method may comprise the controller calculating a scaled quantity following the end of each puff in the session, the scaled quantity dependent on a maximum value of the first quantity during a preceding puff in the session. The method may comprise adjusting the scaled quantity dependent on a time elapsed since an end of the preceding puff. The method may comprise the controller successively reducing the scaled quantity from the maximum value during the preceding puff at regular time intervals following the end of the preceding puff. The method may comprise the controller successively reducing the scaled quantity from the maximum value at regular time intervals following the end of preceding puff by a pre-determined proportion of the maximum value. The method may comprise adjusting the first quantity such that the first quantity is equal to the scaled quantity following the end of the preceding puff in the session and before the start of an ensuing puff in the session.

The method may comprise calculating or determining a first quantity value during each ensuing puff, and adjusting the first quantity during each ensuing puff in the session such that the first quantity is equal to the scaled quantity until the first quantity value exceeds the scaled quantity. The method may comprise adjusting the first quantity during each ensuing puff in the session such that the first quantity is equal to the first quantity value if the first quantity value exceeds the scaled quantity at the start of the ensuing puff. The method may comprise adjusting the first quantity during each ensuing puff in the session such that the first quantity is equal to the scaled quantity unless the first quantity value exceeds the scaled quantity. The method may comprise adjusting the first quantity during each ensuing puff in the session such that the first quantity is equal to the first quantity value if the first quantity value exceeds the scaled quantity at the start of the ensuing puff. The method may comprise adjusting the first quantity during each ensuing puff in the session such that the first quantity is equal to the scaled quantity unless the first quantity value exceeds the scaled quantity. The method may comprise, once the first quantity value exceeds the scaled quantity during the ensuing puff in the session, adjusting the first quantity during the ensuing puff such that the first quantity is equal to the first quantity value. The method may comprise, once the first quantity value exceeds the scaled quantity during the ensuing puff in the session, adjusting the first quantity during the ensuing puff such that the first quantity is equal to the first quantity value for the remainder of the ensuing puff. The method may comprise adjusting, once the first quantity value exceeds the scaled quantity during the ensuing puff in the session, adjusting the first quantity during the ensuing puff dependent on one or more parameters measured or determined by the controller, as disclosed above. Advantageously, this ensures that the more sensitive of thresholds is used to identify whether an adverse condition is present.

The method may comprise calculating or determining the first quantity value during each ensuing puff dependent on the same parameters used to calculate or determine the first quantity during a first puff. That is, the method may comprise calculating or determining the first quantity value during each ensuing puff dependent on the power supplied to the heating element. The method may comprise calculating or determining the first quantity value during each ensuing puff dependent on the pressure or the flow rate measured by the sensor assembly. The method may comprise calculating or determining the first quantity value during each ensuing puff dependent on the total number of puffs elapsed during the session. The method may comprise calculating or determining the first quantity value during each ensuing puff dependent on a total time elapsed since the start of the session. The method may comprise calculating or determining the first quantity value during each ensuing puff dependent on a puff time elapsed since the start of each ensuing puff. The method may comprise linearly increasing the first quantity value during each ensuing puff dependent on a puff time elapsed since the start of each ensuing puff. The method may comprise calculating or determining the first quantity value during each ensuing puff dependent on a time elapsed since an end of the preceding puff in the session. The method may comprise the controller adjusting the first quantity following the end of each puff in the session such that the first quantity is equal to the scaled quantity until the first quantity exceeds the scaled quantity.

The one or more parameters may comprise an ambient temperature. The resistance of the heating element is dependent on the temperature of the heating element. If the ambient temperature of the environment in which the aerosol-generating system is located increases, the temperature of the heating element will also increase, as heat is lost less quickly when the heating element is heated. The resistance of the heating element will therefore increase. Therefore, it is advantageous to adjust the first quantity dependent on the ambient temperature, as more accurate detection of adverse conditions may be achieved. The method may further comprise adjusting the baseline resistance dependent on the ambient temperature.

The aerosol-generating system may comprise an aerosol-generating device and a cartridge, wherein the cartridge is couplable to the aerosol-generating device. The aerosolgenerating device may comprise the controller and the power supply. The cartridge may comprise the heating element. The method may further comprise the step of the controller determining a classification of the cartridge when the cartridge is couple to the aerosol-generating device, and wherein the one or more parameters may comprise the classification of the cartridge. Advantageously, the characteristics of the cartridge may vary dependent on the classification of the cartridge. For example, cartridges may have different heating elements which, display different increases in resistance with temperature. Therefore, it is advantageous to adjust the first quantity dependent on the classification of the cartridge as more accurate detection of adverse conditions may be achieved.

The step of determining the baseline resistance of the heating element may comprise determining the baseline resistance of the heating element after the user couples the cartridge to the aerosol-generating device. The step of determining the baseline resistance of the heating element may comprise determining the baseline resistance of the heating element after one or both of the user switching the aerosol-generating system on, or the user not puffing on the device for a pre-determined cooldown time period. Advantageously, the baseline resistance of the heating element is therefore determined when the heater is sufficiently cool.

The step of continually adjusting the first quantity during the session may comprise continually adjusting the first quantity at regular time intervals during the session. The session of one or more puffs may be a session of a plurality of puffs.

The heating element may comprise a mesh. The aerosol-forming substrate may be a liquid aerosol-forming substrate.

The method may further comprise the step of switching from the first mode to a second mode when the controller determines an adverse condition during one or more puffs.

The method may comprise in the second mode confirming an adverse condition when the resistance exceeds the baseline resistance by a second quantity. The second quantity may be a pre-determined quantity. The second quantity may be a second resistance equal to a proportion of the baseline resistance. The second quantity may be a second resistance equal to a proportion of the first resistance. The second quantity may be different from the first quantity. The method may comprise, in the second mode, the controller controlling the power supplied to the heating element from the power supply. In the second mode, the power supplied to the heating element from the power supply may be constant for the duration of each puff of the session. In the second mode, the power supplied to the heating element from the power supply during each puff of the session many be insufficient for generating aerosol from the aerosol-forming substrate. Advantageously, this feature may prevent the heating element from being overheated when an adverse condition is present at the heating element, such as insufficient liquid supplied to the heating element.

The method may comprise in the second mode the controller switching to the first mode if an adverse condition is not confirmed by the controller within N puffs of the controller switching to the second mode, wherein N is an integer number of puffs. N may be an integer greater than or equal to 1 , and may be less than or equal to 10. N may be an integer greater than or equal to 2, and may be less than or equal to 10. Advantageously, this prevents the controller switching back to the first mode when a reading gave a false-negative result that an adverse condition is not present. The method may comprise in the second mode the controller detecting a change of cartridge, and switching from the second mode to the first mode if a change of cartridge is detected. The step of switching from the first mode to a second mode when the controller determines an adverse condition during one or more puffs may comprise switching from the first mode to a second mode when the controller determines an adverse condition during M puffs, wherein M is an integer greater than or equal to 1 , and may be less than or equal to 10. Advantageously, this feature may prevent the controller from switching to the second mode if only one erroneous reading gave a false-positive result that an adverse condition is present.

The controller may comprise a computer readable memory. The computer readable memory may store a look-up table comprising a plurality of power profiles and a plurality of ranges of pressure or the flow rate Each of the ranges of the pressure or the flow rate may correspond to at least one of the power profiles. The method may comprise in the first mode selecting a power profile from the plurality of power profiles to control the supply of power to the heating element during a puff, the selection dependent on the pressure or the flow rate measured by the sensor assembly. Advantageously, this feature may minimise the amount of calculation required of the controller, reducing the computing power necessary.

The look-up table may further comprise a plurality of system profiles. Each of the power profiles may correspond to one of the ranges of the pressure or the flow rate and one of the system profiles. The step of selecting a power profile from the plurality of power profiles to control the supply of power to the heating element during a puff may be dependent on a system profile selected by a user. Advantageously, this allows the user to control, at least in part, the desired characteristics of the aerosol generation. Each power profile may comprise a plurality of power values. Each of the plurality of power values may correspond to a range of time since the start of a puff. The method may comprise in the first mode controlling the supply of power to the heating element during a puff dependent on the plurality of power values and the time since the start of the puff.

Each power profile may further comprise a plurality of first quantity values. Each of the plurality of first quantity values may correspond to one of the plurality of power values. The step of adjusting the first quantity may comprise adjusting the first quantity dependent on a selected first quantity value from the plurality of first quantity values stored in the look-up table. Advantageously, this feature may eliminate the need for the controller to calculate the first quantity, significantly reducing the computing power necessary. The step of adjusting the first quantity may comprise adjusting the first quantity to be equal to the selected first quantity value stored in the look-up table. The first quantity values are proportions of the baseline resistance. The step of adjusting the first quantity may comprise determining a first resistance value from a product of the selected first quantity value and the baseline resistance. The step of adjusting the first quantity may comprise adjusting the first quantity to be equal to the first resistance value.

Each power profile may further comprise a plurality of first maximum resistance values. Each of the plurality of first maximum resistance values may correspond to one of the plurality of power values and to one of the plurality of first quantity values. The step of adjusting the first quantity may comprise adjusting the first quantity dependent on both the selected first quantity value and a selected first maximum resistance value from the plurality of first maximum resistance values. The step of adjusting the first quantity may comprise adjusting the first quantity to be equal to the lower of the first resistance value and the selected first maximum resistance value. Advantageously, this may prevent the first quantity being too high, and hence the method not being sufficiently sensitive to adverse conditions, in the event that the baseline resistance is particularly high.

As used herein with reference to the invention, the term “aerosol” is used to describe a dispersion of solid particles, or liquid droplets, or a combination of solid particles and liquid droplets, in a gas. The aerosol may be visible or invisible. The aerosol may include vapours of substances that are ordinarily liquid or solid at room temperature as well as solid particles, or liquid droplets, or a combination of solid particles and liquid droplets.

As used herein, an “aerosol-generating system” means a system that generates an aerosol from one or more aerosol-forming substrates.

As used herein, the term “aerosol-forming substrate” means a substrate capable of releasing volatile compounds that may form an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. As used herein, the term “puff’ is used to describe the action of a user generating aerosol using the aerosol-generating system. The user carries out this action by drawing air through the aerosol-generating system by inhalation.

As used herein, the term “session” refers to a period in which the aerosol-generating system is activated, for example by a user, and comprises at least one puff. During the session, the aerosolgenerating system may automatically detect a puff, as described above, and power the heating element accordingly.

As used herein, the term “puff number” refers to the number assigned to the puff of a session based on the total number of discreet puffs preceding the puff.

As used herein, the term “cumulative puffing time” refers to the total time elapsed during each discreet puff so far during a session of at least one puff.

As used herein, the term “look-up table” refers to a table or a matrix stored in the computer readable memory, accessible by the controller, and from which the controller may retrieve values.

As used herein, the term “power profile” refers to a look-up table comprising at least one power value and associated duration(s) for which the at least one power values are sequentially applied.

As used herein, the terms “air inlet’ and ‘air outlet” are used to describe one or more apertures through which air may be drawn into, and out of, respectively, of a component or portion of a component of the cartridge, aerosol-generating system or aerosol-generating device.

As used herein, the term “cartridge” also refers to an article comprising an aerosol-forming substrate that is capable of releasing volatile compounds that can form an aerosol. A cartridge also may be disposable.

A cartridge may contain a liquid. The liquid may comprise volatile compounds that may form an aerosol. The liquid may form an aerosol upon heating of the liquid. The aerosol-forming substrate may be a liquid. The aerosol-forming substrate may be a liquid at room temperature. The aerosolforming substrate may be in another condensed form, such as a solid at room temperature, or may be in another condensed form, such as a gel, at room temperature. Volatile compounds may be released by heating the aerosol-forming substrate. The aerosol-forming substrate may comprise both liquid and solid components. The liquid aerosol-forming substrate may comprise nicotine. The nicotine containing liquid aerosol-forming substrate may be a nicotine salt matrix. The liquid aerosol-forming substrate may comprise plant-based material. The liquid aerosol-forming substrate may comprise tobacco. The liquid aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavour compounds, which are released from the aerosol-forming substrate upon heating. The liquid aerosol-forming substrate may comprise homogenised tobacco material. The liquid aerosol-forming substrate may comprise a non-tobacco-containing material. The liquid aerosolforming substrate may comprise homogenised plant-based material.

The liquid aerosol-forming substrate may comprise one or more aerosol-formers. An aerosolformer is any suitable known compound or mixture of compounds that, in use, facilitates formation of a dense and stable aerosol and that is substantially resistant to thermal degradation at the temperature of operation of the system. Examples of suitable aerosol formers include glycerine and propylene glycol. Suitable aerosol-formers are well known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, 1 ,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. The liquid aerosol-forming substrate may comprise water, solvents, ethanol, plant extracts and natural or artificial flavours. The liquid aerosolforming substrate may comprise nicotine and at least one aerosol former. The aerosol former may be glycerine or propylene glycol. The aerosol former may comprise both glycerine and propylene glycol. The liquid aerosol-forming substrate may have a nicotine concentration of between about 0.5% and about 10%, for example about 2%.

The heating element may be configured to be resistively heated by the application of an electrical current through the heating element. The heating element may be configured to be inductively heated by currents induced in the heating element by a varying magnetic field. The heating element may be configured to be inductively heated by hysteresis effects.

The heating element may take a form suitable for heating the aerosol-forming substrate. In some embodiments the heating element is fluid permeable. The heating element may comprise a plurality of electrically conductive filaments. The aerosol-generating element may comprise fluid permeable mesh. The heating element may comprise a plurality of interstices or apertures extending from the second side to the first side and through which fluid may pass. The heating element may be an array of filaments, for example arranged parallel to each other. Preferably, the filaments may form a mesh. Alternatively, the electrically conductive heating element consists of an array of filaments or a fabric of filaments. The electrically conductive filaments may define interstices between the filaments and the interstices may have a width of between 10 micrometres and 100 micrometres. Preferably, the filaments give rise to capillary action in the interstices, so that in use, liquid to be vaporized is drawn into the interstices, increasing the contact area between the heating element and the liquid aerosol-forming substrate.

The electrically conductive filaments may have a diameter of between 8 micrometres and 100 micrometres, preferably between 10 micrometres and 50 micrometres, more preferably between 12 micrometres and 25 micrometres, and most preferably approximately 16 micrometres. The filaments may have a round cross section or may have a flattened cross-section.

The aerosol-generating element may be configured to be resistively heated. In other words, the aerosol-generating element may be configured to generate heat when an electrical current is passed though the heating element. The heating element, or portions thereof, may comprise or be formed from any material with suitable electrical and mechanical properties, for example a suitable, electrically resistive material. Suitable materials include but are not limited to: semiconductors such as doped ceramics, electrically “conductive” ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys and composite materials made of a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum and metals from the platinum group.

The electrical resistance of the mesh, array or fabric of electrically conductive filaments of the heater element is preferably between 0.3 and 4 Ohms. More preferably, the electrical resistance of the mesh, array or fabric of electrically conductive filaments is between 0.5 and 3 Ohms, and more preferably about 1 Ohm. Preferably, the electrical resistance is equal or greater than 0.5 Ohms. More preferably, the electrical resistance of the mesh, array or fabric of electrically conductive filaments is between 0.6 Ohms and 0.8 Ohms, and most preferably about 0.68 Ohms. Alternatively, the heating element may comprise a heating plate in which an array of apertures is formed. The apertures may be formed by etching or machining, for example. The plate may be formed from any material with suitable electrical properties, such as the materials described above in relation to filaments of a heating element.

The aerosol-generating device may comprise a power supply, for example a battery. The power supply may be a DC power supply. The power supply may be a battery. The battery may be a Lithium based battery, for example a Lithium-Cobalt, a Lithium-lron-Phosphate, a Lithium Titanate or a Lithium-Polymer battery. The battery may be a Nickel metal hydride battery or a Nickel cadmium battery. The power supply may be another form of charge storage device such as a capacitor.

The power supply may be connected to the heating element. The aerosol-generating device may comprise a controller. The controller may be connected to the power source. The controller may be connected to the heating element. The controller may control the supply of power from the power source to the heating element. The controller may control a temperature of the heating element. The controller may comprise a microcontroller. The microcontroller may be a programmable microcontroller.

The aerosol-generating system may be a handheld aerosol-generating system. The aerosolgenerating system may be a handheld aerosol-generating system configured to allow a user to suck on a mouthpiece to draw an aerosol through a first air outlet. The aerosol-generating system may have a size comparable to a conventional cigar or cigarette. The aerosol-generating system may have a total length between about 25 mm and about 150 mm. The aerosol-generating system may have an external diameter between about 5 mm and about 30mm.

The invention is defined in the claims. However, below there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein. Example Ex1. An aerosol-generating system comprising: a heating element for heating an aerosol-forming substrate; a power supply for supplying power to the heating element; and a controller, the controller configured to: in a first mode, control the power to the heating element from the power supply; measure or determine a baseline resistance of the heating element; measure the resistance of the heating element during a session of one or more puffs; compare the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance; and determine an adverse condition when the resistance exceeds the baseline resistance by a first quantity; wherein in the first mode the controller is configured to continually adjust the first quantity during the session dependent on one or more parameters measured or determined by the controller.

Example Ex2. An aerosol-generating system according to any preceding Example, wherein the aerosol-generating system is configured to display a warning to a user when the controller determines an adverse condition during one or more puffs.

Example Ex3. An aerosol-generating system according to any preceding Example, wherein the controller is configured to stop or reduce power supplied to the heating element when the controller determines an adverse condition during one or more puffs.

Example Ex4. An aerosol-generating system according to any preceding Example, wherein the controller is configured to measure the resistance of the heating element at regular time intervals during the session of one or more puffs.

Example Ex5. An aerosol-generating system according to Example Ex4, wherein the controller is configured to compare the resistance of the heating element to the baseline resistance or a threshold based on the baseline resistance at regular time intervals during the session of one or more puffs.

Example Ex6. An aerosol-generating system according to any preceding Example, wherein the controller is configured to adjust the first quantity during each of the one or more puffs dependent on the power supplied to the heating element.

Example Ex7. An aerosol-generating system according to any preceding Example, wherein the aerosol-generating system further comprises an air inlet and an air outlet; and an air flow passage extending between the air inlet and the air outlet.

Example Ex8. An aerosol-generating system according to Example Ex7, wherein the aerosolgenerating system further comprises a sensor assembly in communication with the air flow passage, the sensor assembly being configured to measure a pressure or a flow rate within the airflow passage.

Example Ex9. An aerosol-generating system according to Example Ex8, wherein the controller is configured to adjust the first quantity during each of the one or more puffs dependent on the pressure or the flow rate measured by the sensor assembly. Example Ex10. An aerosol-generating system according to Example Ex8 or Ex9, wherein the controller is configured to detect a start of a puff when a user puffs on the aerosolgenerating system based on the pressure or the flow rate measured by the sensor assembly.

Example Ex11 . An aerosol-generating system according to any preceding Example, wherein the controller is configured to adjust the first quantity dependent on the total number of puffs elapsed during the session.

Example Ex12. An aerosol-generating system according to any preceding Example, wherein the controller is configured to adjust the first quantity dependent on a total time elapsed since the start of the session.

Example Ex13. An aerosol-generating system according to any preceding Example, wherein the controller is configured to adjust the first quantity during each of the one or more puffs dependent on a puff time elapsed since the start of each of the one or more puffs.

Example Ex14. An aerosol-generating system according to Example Ex13, wherein the controller is configured to linearly increase the first quantity during each of the one or more puffs dependent on a puff time elapsed since the start of each of the one or more puffs

Example Ex15. An aerosol-generating system according to any preceding Example, wherein the controller is configured to adjust the first quantity dependent on a time elapsed since an end of a preceding puff in the session.

Example Ex16. An aerosol-generating system according to any of Examples Ex1 to Ex15, wherein the controller is configured to calculate a scaled quantity following the end of each puff in the session, the scaled quantity dependent on a maximum value of the first quantity during a preceding puff in the session, and adjust the scaled quantity dependent on a time elapsed since an end of the preceding puff.

Example Ex17. An aerosol-generating system according to Example Ex16, wherein the controller is configured to successively reduce the scaled quantity from the maximum value during the preceding puff at regular time intervals following the end of the preceding puff.

Example Ex18. An aerosol-generating system according to Example Ex17, wherein the controller is configured to successively reduce the scaled quantity from the maximum value at regular time intervals following the end of preceding puff by a pre-determined proportion of the maximum value.

Example Ex19. An aerosol-generating system according to any of Examples Ex16 to Ex18, wherein the controller is configured to adjust the first quantity such that the first quantity is equal to the scaled quantity following the end of the preceding puff in the session and before the start of an ensuing puff in the session.

Example Ex20. An aerosol-generating system according to Example Ex19, wherein the controller is configured to calculate or determine a first quantity value during each ensuing puff, and the controller is further configured to adjust the first quantity during each ensuing puff in the session such that the first quantity is equal to the scaled quantity until the first quantity value exceeds the scaled quantity.

Example Ex21. An aerosol-generating system according to Example Ex20, wherein the controller is configured to calculate or determine the first quantity value during each ensuing puff dependent on the power supplied to the heating element.

Example Ex22. An aerosol-generating system according to Example Ex20 or Ex21 when dependent on Example Ex8, wherein the controller is configured to calculate or determine the first quantity value during each ensuing puff dependent on the pressure or the flow rate measured by the sensor assembly.

Example Ex23. An aerosol-generating system according to any of Examples Ex20 to Ex22, wherein the controller is configured to calculate or determine the first quantity value during each ensuing puff dependent on the total number of puffs elapsed during the session.

Example Ex24. An aerosol-generating system according to any of Examples Ex20 to Ex23, wherein the controller is configured to calculate or determine the first quantity value during each ensuing puff dependent on a total time elapsed since the start of the session.

Example Ex25. An aerosol-generating system according to any of Examples Ex20 to Ex24, wherein the controller is configured to calculate or determine the first quantity value during each ensuing puff dependent on a puff time elapsed since the start of each ensuing puff.

Example Ex26. An aerosol-generating system according to Example Ex25, wherein the controller is configured to linearly increase the first quantity value during each ensuing puff dependent on a puff time elapsed since the start of each ensuing puff.

Example Ex27. An aerosol-generating system according to any of Examples Ex20 to Ex26, wherein the controller is configured to calculate or determine the first quantity value during each ensuing puff dependent on a time elapsed since an end of the preceding puff in the session.

Example Ex28. An aerosol-generating system according to any preceding Example, wherein the controller is configured to adjust the first quantity dependent on an ambient temperature.

Example Ex29. An aerosol-generating system according to any preceding Example, wherein the aerosol-generating system comprises an aerosol-generating device and a cartridge, wherein the cartridge is couplable to the aerosol-generating device.

Example Ex30. An aerosol-generating system according to Example Ex29, wherein the aerosol-generating device comprises the controller and the power supply.

Example Ex31. An aerosol-generating system according to Example Ex29 or Ex30, wherein the cartridge comprises the heating element. Example Ex32. An aerosol-generating system according to Example Ex31 , wherein the controller is configured to determine a classification of the cartridge when the cartridge is couple to the aerosol-generating device, and wherein the controller is configured to adjust the first quantity dependent on the classification of the cartridge.

Example Ex33. An aerosol-generating system according to any of Examples Ex29 to Ex32, wherein the controller is configured to determine the baseline resistance of the heating element after the user couples the cartridge to the aerosol-generating device.

Example Ex34. An aerosol-generating system according to any preceding Example, wherein the controller is configured to determine the baseline resistance of the heating element after one or both of the user switching the aerosol-generating system on, or the user not puffing on the device for a pre-determined cooldown time period.

Example Ex35. An aerosol-generating system according to any preceding Example, wherein the first quantity is a first resistance equal to a proportion of the baseline resistance.

Example Ex36. An aerosol-generating system according to any preceding Example, wherein the controller is configured to continually adjust the first quantity at regular time intervals during the session.

Example Ex37. An aerosol-generating system according to any preceding Example, wherein the session of one or more puffs is a session of a plurality of puffs.

Example Ex38. An aerosol-generating system according to any preceding Example, wherein the heating element comprises a mesh.

Example Ex39. An aerosol-generating system according to any preceding Example, wherein the aerosol-forming substrate is a liquid or gel aerosol-forming substrate.

Example Ex40. An aerosol-generating system according to any preceding Example, wherein when the controller determines an adverse condition during one or more puffs, the controller is configured to switch from the first mode to a second mode.

Example Ex41. An aerosol-generating system according to Example Ex40, wherein in the second mode the controller is configured to confirm an adverse condition when the resistance exceeds the baseline resistance by a second quantity.

Example Ex42. An aerosol-generating system according to Example Ex41 , wherein the second quantity is a second resistance equal to a proportion of the baseline resistance.

Example Ex43. An aerosol-generating system according to any of Examples Ex40 to Ex42, wherein in the second mode the controller is configured to control the power supplied to the heating element from the power supply.

Example Ex44. An aerosol-generating system according to Example Ex43, wherein in the second mode, the power supplied to the heating element from the power supply is constant for the duration of each puff of the session. Example Ex45. An aerosol-generating system according to Example Ex43 or Ex44, wherein in the second mode, the power supplied to the heating element from the power supply during each puff of the session is insufficient for generating aerosol from the aerosol-forming substrate.

Example Ex46. An aerosol-generating system according to any of Examples Ex40 to Ex 45, wherein in the second mode the controller is configured to switch to the first mode if an adverse condition is not confirmed by the controller within N puffs of the controller switching to the second mode, wherein N is an integer number of puffs.

Example Ex47. An aerosol-generating system according to Example Ex46, wherein N is an integer greater than or equal to 1 , and less than or equal to 10.

Example Ex48. An aerosol-generating system according to any of Examples Ex40 to Ex46 when dependent on Ex29, wherein the controller is configured detect a change of cartridge, and configured to switch from the second mode to the first mode if a change of cartridge is detected .

Example Ex49. An aerosol-generating system according to any of Examples Ex40 to Ex48, wherein when the controller determines an adverse condition during M puffs, the controller is configured to switch from the first mode to a second mode, wherein M is an integer greater than or equal to 1 , and less than or equal to 10.

Example Ex50. An aerosol-generating system according to any preceding Example, wherein the controller comprises a computer readable memory.

Example Ex51. An aerosol-generating system according to Example Ex50 when dependent on Ex8, wherein the computer readable memory stores a look-up table comprising a plurality of power profiles and a plurality of ranges of pressure or the flow rate, wherein each of the ranges of the pressure or the flow rate correspond to at least one of the power profiles, and wherein the controller is further configured in the first mode to select a power profile from the plurality of power profiles to control the supply of power to the heating element during a puff, the selection dependent on the pressure or the flow rate measured by the sensor assembly.

Example Ex52. An aerosol-generating system according to Example Ex51 , wherein the look-up table further comprises a plurality of system profiles, wherein each of the power profiles correspond to one of the ranges of the pressure or the flow rate and one of the system profiles, and wherein the controller is configured in the first mode to select a power profile from the plurality of power profiles to control the supply of power to the heating element during a puff, the selection dependent on the pressure or the flow rate measured by the sensor assembly and a system profile selected by a user. Example Ex53. An aerosol-generating system according to Example Ex51 or Ex52, wherein each power profile comprises a plurality of power values, and each of the plurality of power values corresponding to a range of time since the start of a puff , and wherein the controller is configured in the first mode to control the supply of power to the heating element during a puff dependent on the plurality of power values and the time since the start of the puff.

Example Ex54. An aerosol-generating system according to Example Ex53, wherein each power profile further comprises a plurality of first quantity values, wherein each of the plurality of first quantity values correspond to one of the plurality of power values.

Example Ex55. An aerosol-generating system according to Example Ex54, wherein the controller is configured to adjust the first quantity dependent on a selected first quantity value from the first quantity values stored in the look-up table.

Example Ex56. An aerosol-generating system according to Example Ex55, wherein the controller is configured to adjust the first quantity to be equal to the selected first quantity value.

Example Ex57. An aerosol-generating system according to any of Examples Ex54 to Ex56, wherein the first quantity values are proportions of the baseline resistance.

Example Ex58. An aerosol-generating system according to Example Ex57, wherein the controller is configured to determine a first resistance value from a product of the selected first quantity value and the baseline resistance.

Example Ex59. An aerosol-generating system according to Example Ex58, wherein the controller is configured to adjust the first quantity to be equal to the first resistance value.

Example Ex60. An aerosol-generating system according to Example Ex55, wherein each power profile further comprises a plurality of first maximum resistance values, wherein each of the plurality of first maximum resistance values correspond to one of the plurality of power values and to one of the plurality of first quantity values, and wherein the controller is configured to adjust the first quantity dependent on both the selected first quantity value and a selected first maximum resistance value from the plurality of first maximum resistance values.

Example Ex61. An aerosol-generating system according to Example Ex60, wherein the controller is configured to adjust the first quantity to be equal to the lower of the first resistance value and the selected first maximum resistance value.

Example Ex62. A method of determining an adverse condition in an aerosol-generating system, the aerosol-generating system comprising: a heating element for heating an aerosol-forming substrate; a power supply for supplying power to the heating element; and a controller, the method comprising the steps of: in a first mode, controlling the power to the heating element from the power supply; measuring or determining a baseline resistance of the heating element; measuring the resistance of the heating element during a session of one or more puffs; comparing the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance; determining an adverse condition when the resistance exceeds the baseline resistance by a first quantity; and continually adjusting the first quantity during the session dependent on one or more parameters measured or determined by the controller.

Example Ex63. A method according to Example Ex62, wherein the method further comprises the step of displaying a warning to a user when the controller determines an adverse condition during one or more puffs.

Example Ex64. A method according to Example Ex62 or Ex63, wherein the method further comprises the step of stopping or reducing power supplied to the heating element when the controller determines an adverse condition during one or more puffs.

Example Ex65. A method according to any of Examples Ex62 to Ex64, wherein measuring the resistance of the heating element during a session of one or more puffs comprises measuring the resistance of the heating element at regular time intervals during the session of one or more puffs.

Example Ex66. A method according to Example Ex65, wherein comparing the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance comprises comparing the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance at regular time intervals during the session of one or more puffs.

Example Ex67. A method according to any of Examples Ex62 to Ex66, wherein the one or more parameters comprises the power supplied to the heating element.

Example Ex68. A method according to any one of Examples Ex62 to Ex 67, wherein the aerosol-generating system further comprises an air inlet and an air outlet; and an air flow passage extending between the air inlet and the air outlet.

Example Ex69. A method according to Example Ex68, wherein the aerosol-generating system further comprises a sensor assembly in communication with the air flow passage, the sensor assembly being configured to measure a pressure or a flow rate within the airflow passage. Example Ex70. A method according to Example Ex69, wherein the one or more parameters comprises the pressure or the flow rate measured by the sensor assembly.

Example Ex71. A method according to Example Ex69 or Ex70, wherein the controller is configured to detect the start of a puff when a user puffs on the aerosol-generating system based on the pressure or the flow rate measured by the sensor assembly.

Example Ex72. A method according to any one of Example Ex62 to Ex71 , wherein the one or more parameters comprises a total number of puffs elapsed during the session.

Example Ex73. A method according to any one of Example Ex62 to Ex72, wherein the one or more parameters comprises a total time elapsed since the start of the session.

Example Ex74. A method according to any one of Example Ex62 to Ex73, wherein the one or more parameters comprises a puff time elapsed since the start of each of the one or more puffs.

Example Ex75. A method according to Example Ex74, wherein continually adjusting the first quantity during the session dependent on the puff time elapsed since the start of each of the one or more puffs comprises linearly increasing the first quantity during each of the one or more puffs dependent on a puff time elapsed since the start of each of the one or more puffs.

Example Ex76. A method according to any one of Example Ex62 to Ex75wherein the one or more parameters comprises a time elapsed since an end of a preceding puff in the session.

Example Ex77. A method according to any of Examples Ex62 to Ex76, wherein the method comprises the controller calculating a scaled quantity following the end of each puff in the session, the scaled quantity dependent on a maximum value of the first quantity during a preceding puff in the session, and adjusting the scaled quantity dependent on a time elapsed since an end of the preceding puff.

Example Ex78. A method according to Example Ex77, wherein the method comprises the controller successively reducing the scaled quantity from the maximum value during the preceding puff at regular time intervals following the end of the preceding puff.

Example Ex79. A method according to Example Ex78, wherein the method comprises the controller successively reducing the scaled quantity from the maximum value at regular time intervals following the end of preceding puff by a pre-determined proportion of the maximum value.

Example Ex80. A method according to any one of Examples Ex77 to Ex79, wherein the method comprises adjusting the first quantity such that the first quantity is equal to the scaled quantity following the end of the preceding puff in the session and before the start of an ensuing puff in the session. Example Ex81. A method according to Example Ex80, wherein the method comprises calculating or determining a first quantity value during each ensuing puff, and adjusting the first quantity during each ensuing puff in the session such that the first quantity is equal to the scaled quantity until the first quantity value exceeds the scaled quantity.

Example Ex82. A method according to Example Ex81 , wherein the method comprises calculating or determining the first quantity value during each ensuing puff dependent on the power supplied to the heating element.

Example Ex83. A method according to Example Ex81 or Ex82 when dependent on Ex69, wherein the method comprises calculating or determining the first quantity value during each ensuing puff dependent on the pressure or the flow rate measured by the sensor assembly.

Example Ex84. A method according to any of Examples Ex81 to Ex83, wherein the method comprises calculating or determining the first quantity value during each ensuing puff dependent on the total number of puffs elapsed during the session.

Example Ex85. A method according to any of Examples Ex81 to Ex84, wherein the method comprises calculating or determining the first quantity value during each ensuing puff dependent on a total time elapsed since the start of the session.

Example Ex86. A method according to any of Examples Ex81 to Ex85, wherein the method comprises calculating or determining the first quantity value during each ensuing puff dependent on a puff time elapsed since the start of each ensuing puff.

Example Ex87. A method according to Example Ex86, wherein the method comprises linearly increasing the first quantity value during each ensuing puff dependent on a puff time elapsed since the start of each ensuing puff.

Example Ex88. A method according to any of Examples Ex81 to Ex87, wherein the method comprises calculating or determining the first quantity value during each ensuing puff dependent on a time elapsed since an end of the preceding puff in the session.

Example Ex89. A method according to any one of Examples Ex81 to Ex88, wherein the method comprises the controller adjusting the first quantity following the end of each puff in the session such that the first quantity is equal to the scaled quantity until the first quantity exceeds the scaled quantity.

Example Ex90. A method according to any one of Examples Ex62 to Ex89, wherein the one or more parameters comprises an ambient temperature.

Example Ex91 . A method according to any one of Examples Ex62 to Ex90, wherein the aerosol-generating system comprises an aerosol-generating device and a cartridge, wherein the cartridge is couplable to the aerosol-generating device.

Example Ex92. A method according to Example Ex91 , wherein the aerosol-generating device comprises the controller and the power supply. Example Ex93. A method according to Example Ex91 or Ex92, wherein the cartridge comprises the heating element.

Example Ex94. A method according to Example Ex93, wherein the method further comprises the step of the controller determining a classification of the cartridge when the cartridge is couple to the aerosol-generating device, and wherein the one or more parameters comprises the classification of the cartridge.

Example Ex95. A method according to any of Examples Ex91 to Ex94, wherein the step of determining the baseline resistance of the heating element comprises determining the baseline resistance of the heating element after the user couples the cartridge to the aerosolgenerating device.

Example Ex96. A method according to any one of Examples Ex62 to Ex95, wherein the step of determining the baseline resistance of the heating element comprises determining the baseline resistance of the heating element after one or both of the user switching the aerosolgenerating system on, or the user not puffing on the device for a pre-determined cooldown time period.

Example Ex97. A method according to any one of Examples Ex62 to Ex96, wherein the first quantity is a first resistance equal to a proportion of the baseline resistance.

Example Ex98. A method according to any one of Examples Ex62 to Ex97, wherein the step of continually adjusting the first quantity during the session comprises continually adjusting the first quantity at regular time intervals during the session.

Example Ex99. A method according to any one of Examples Ex62 to Ex98, wherein the session of one or more puffs is a session of a plurality of puffs.

Example Ex100. A method according to any one of Examples Ex62 to Ex99, wherein the heating element comprises a mesh.

Example Ex101. A method according to any one of Examples Ex62 to Ex100, wherein the aerosol-forming substrate is a liquid aerosol-forming substrate.

Example Ex102. A method according to any one of Examples Ex62 to Ex101 , wherein the method further comprises the step of switching from the first mode to a second mode when the controller determines an adverse condition during one or more puffs.

Example Ex103. A method according to Example Ex102, wherein the method comprises in the second mode confirming an adverse condition when the resistance exceeds the baseline resistance by a second quantity.

Example Ex104. A method according to Example Ex103, wherein the second quantity is a second resistance equal to a proportion of the baseline resistance. Example Ex105. A method according to Example Ex103 or Ex104, wherein the method comprises in the second mode the controller controlling the power supplied to the heating element from the power supply.

Example Ex106. A method according to Example Ex105, wherein in the second mode, the power supplied to the heating element from the power supply is constant for the duration of each puff of the session.

Example Ex107. A method according to Example Ex105 or Ex106, wherein in the second mode, the power supplied to the heating element from the power supply is during each puff of the session is insufficient for generating aerosol from the aerosol-forming substrate.

Example Ex108. A method according to any one of Examples Ex102 to Ex107, wherein the method comprises in the second mode the controller switching to the first mode if an adverse condition is not confirmed by the controller within N puffs of the controller switching to the second mode, wherein N is an integer number of puffs.

Example Ex109. A method according to Example Ex108, wherein N is an integer greater than or equal to 1 , and less than or equal to 10.

Example Ex110. A method according to any of Examples Ex102 to Ex109 when dependent on Ex91 , wherein the method comprises in the second mode the controller detecting a change of cartridge, and switching from the second mode to the first mode if a change of cartridge is detected.

Example Ex111. A method according to any of Examples Ex102 to Ex110, wherein the step of switching from the first mode to a second mode when the controller determines an adverse condition during one or more puffs comprises switching from the first mode to a second mode when the controller determines an adverse condition during M puffs, wherein M is an integer greater than or equal to 1 , and less than or equal to 10.

Example Ex112. A method according to any of Examples Ex62 to Ex111 , wherein the controller comprises a computer readable memory.

Example Ex113. A method according to Example Ex112 when dependent on Ex69, wherein the computer readable memory stores a look-up table comprising a plurality of power profiles and a plurality of ranges of pressure or the flow rate, wherein each of the ranges of the pressure or the flow rate correspond to at least one of the power profiles, and wherein the method comprises in the first mode selecting a power profile from the plurality of power profiles to control the supply of power to the heating element during a puff, the selection dependent on the pressure or the flow rate measured by the sensor assembly.

Example Ex114. A method according to Example Ex113, wherein the look-up table further comprises a plurality of system profiles, wherein each of the power profiles correspond to one of the ranges of the pressure or the flow rate and one of the system profiles, and wherein in the step of selecting a power profile from the plurality of power profiles to control the supply of power to the heating element during a puff, the selection is also dependent on a system profile selected by a user.

Example Ex115. A method according to Example Ex113 or Ex114, wherein each power profile comprises a plurality of power values, and each of the plurality of power values corresponding to a range of time since the start of a puff, and wherein the method comprises in the first mode controlling the supply of power to the heating element during a puff dependent on the plurality of power values and the time since the start of the puff.

Example Ex116. A method according to Example Ex115, wherein each power profile further comprises a plurality of first quantity values, wherein each of the plurality of first quantity values correspond to one of the plurality of power values.

Example Ex117. A method according to Example Ex116, wherein the step of adjusting the first quantity comprises adjusting the first quantity dependent on a selected first quantity value from the plurality of first quantity values stored in the look-up table.

Example Ex118. A method according to Example Ex117, wherein the step of adjusting the first quantity comprises adjusting the first quantity to be equal to the selected first quantity value stored in the look-up table.

Example Ex119. A method according to any one of Examples Ex116 to Ex118, wherein the first quantity values are proportions of the baseline resistance.

Example Ex120. A method according to Example Ex119, wherein the step of adjusting the first quantity comprises determining a first resistance value from a product of the selected first quantity value and the baseline resistance.

Example Ex121. A method according to Example Ex120, wherein the step of adjusting the first quantity comprises adjusting the first quantity to be equal to the first resistance value.

Example Ex122. A method according to Example Ex117, wherein each power profile further comprises a plurality of first maximum resistance values, wherein each of the plurality of first maximum resistance values correspond to one of the plurality of power values and to one of the plurality of first quantity values, and wherein the step of adjusting the first quantity comprises adjusting the first quantity dependent on both the selected first quantity value and a selected first maximum resistance value from the plurality of first maximum resistance values.

Example Ex123. A method according to Example Ex122, wherein the step of adjusting the first quantity comprises adjusting the first quantity to be equal to the lower of the first resistance value and the selected first maximum resistance value.

Examples will now be further described with reference to the figures in which: Figures 1a to 1d are schematic illustrations of a system in accordance with an embodiment of the invention;

Figure 2 is an exploded view of a cartridge for use in a system as shown in Figures 1a to 1d;

Figure 3 is a detailed view of the filaments of the heater, showing a meniscus of liquid aerosol-forming substrate between the filaments;

Figures 4a and 4b are schematic illustrations of the change of resistance of the heater during a user puff;

Figure 5 is an electric circuit diagram showing how the heating element resistance may be measured;

Figure 6 is flow chart illustrating a method for determining an adverse condition in an aerosol-generating system;

Figure 7a is a table showing a plurality of power profiles, each power profile associated with a system profile value and a pressure difference range;

Figure 7b is a table showing one of the plurality of power profiles;

Figure 8 is a graph showing the variation in the first quantity during a sequence of two puffs;

Figure 9a is a graph showing the variation in the first quantity during a sequence of four puffs, and the corresponding measured variations in resistance of the heating element; and

Figure 9b a graph showing the variation in pressure drop and power supplied to the heating element during the sequence of the four puffs as shown in Figure 9a.

For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 10% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Figures 1a to 1d are schematic illustrations of an aerosol-generating system, including a cartridge in accordance with an embodiment of the invention. Figure 1a is a schematic view of an aerosol-generating device 10 and a separate cartridge 20, which together form the aerosol- generating system. In this example, the aerosol-generating system is an electrically operated smoking system.

The cartridge 20 contains an aerosol-forming substrate and is configured to be received in a cavity 18 within the device. Cartridge 20 should be replaceable by a user when the aerosolforming substrate provided in the cartridge is depleted. Figure 1a shows the cartridge 20 just prior to insertion into the device, with the arrow 1 in Figure 1a indicating the direction of insertion of the cartridge.

The aerosol-generating device 10 is portable and has a size comparable to a conventional cigar or cigarette. The device 10 comprises a main body 11 and a mouthpiece portion 12. The main body 11 contains a battery 14, such as a lithium iron phosphate battery, electric circuitry 16 and a cavity 18. The electric circuitry 16 comprises a programmable microprocessor. The mouthpiece portion 12 is connected to the main body 11 by a hinged connection 21 and can move between an open position as shown in Figure 1 and a closed position as shown in Figure 1d. The mouthpiece portion 12 is placed in the open position to allow for insertion and removal of cartridges 20 and is placed in the closed position when the system is to be used to generate aerosol. The mouthpiece portion comprises a plurality of air inlets 13 and an outlet 15. In use, a user sucks or puffs on the outlet to draw air from the air inlets 13, through the mouthpiece portion to the outlet 15, and thereafter into the mouth or lungs of the user. Internal baffles 17 are provided to force the air flowing through the mouthpiece portion 12 past the cartridge.

The cavity 18 has a circular cross-section and is sized to receive a housing 24 of the cartridge 20. Electrical connectors 19 are provided at the sides of the cavity 18 to provide an electrical connection between the control electronics 16 and battery 14 and corresponding electrical contacts on the cartridge 20.

Figure 1 b shows the system of Figure 1a with the cartridge inserted into the cavity 18, and the cover 26 being removed. In this position, the electrical connectors rest against the electrical contacts on the cartridge.

Figure 1c shows the system of Figure 1b with the cover 26 fully removed and the mouthpiece portion 12 being moved to a closed position.

Figure 1d shows the system of Figure 1c with the mouthpiece portion 12 in the closed position. The mouthpiece portion 12 is retained in the closed position by a clasp mechanism. The mouthpiece portion 12 in a closed position retains the cartridge in electrical contact with the electrical connectors 19 so that a good electrical connection is maintained in use, whatever the orientation of the system is.

Figure 2 is an exploded view of the cartridge 20. The cartridge 20 comprises a generally circular cylindrical housing 24 that has a size and shape selected to be received into the cavity 18. The housing contains capillary material 27, 28 that is soaked in a liquid aerosol-forming substrate. In this example the aerosol-forming substrate comprises 39% by weight glycerine, 39% by weight propylene glycol, 20% by weight water and flavourings, and 2% by weight nicotine. A capillary material is a material that actively conveys liquid from one end to another, and may be made from any suitable material. In this example the capillary material is formed from polyester.

The housing has an open end to which a heater assembly 30 is fixed. The heater assembly 30 comprises a substrate 34 having an aperture 35 formed in it, a pair of electrical contacts 32 fixed to the substrate and separated from each other by a gap 33, and a plurality of electrically conductive heater filaments 36 spanning the aperture and fixed to the electrical contacts on opposite sides of the aperture 35.

The heater assembly 30 is covered by a removable cover 26. The cover comprises a liquid impermeable plastic sheet that is glued to the heater assembly but which can be easily peeled off. A tab is provided on the side of the cover to allow a user to grasp the cover when peeling it off. It will now be apparent to one of ordinary skill in the art that although gluing is described as the method to a secure the impermeable plastic sheet to the heater assembly, other methods familiar to those in the art may also be used including heat sealing or ultrasonic welding, so long as the cover may easily be removed by a consumer.

There are two separate capillary materials 27, 28 in the cartridge of Figure 2. A disc of a first capillary material 27 is provided to contact the heater element 36, 32 in use. A larger body of a second capillary material 28 is provided on an opposite side of the first capillary material 27 to the heater assembly. Both the first capillary material and the second capillary material retain liquid aerosol-forming substrate. The first capillary material 27, which contacts the heater element, has a higher thermal decomposition temperature (at least 160°C or higher such as approximately 250 °C) than the second capillary material 28. The first capillary material 27 effectively acts as a spacer separating the heater element 36, 32 from the second capillary material 28 so that the second capillary material is not exposed to temperatures above its thermal decomposition temperature. The thermal gradient across the first capillary material is such that the second capillary material is exposed to temperatures below its thermal decomposition temperature. The second capillary material 28 may be chosen to have superior wicking performance to the first capillary material 27, may retain more liquid per unit volume than the first capillary material and may be less expensive than the first capillary material. In this example the first capillary material is a heat resistant material, such as a fiberglass or fiberglass containing material and the second capillary material is a polymer such as suitable capillary material. Exemplary suitable capillary materials include the capillary materials discussed herein and in alternative embodiments may include high density polyethylene (HDPE), or polyethylene terephthalate (PET).

The capillary material 27, 28 is advantageously oriented in the housing 24 to convey liquid to the heater assembly 30. When the cartridge is assembled, the heater filaments 36, 37, 38 may be in contact with the capillary material 27 and so aerosol-forming substrate can be conveyed directly to the mesh heater. Figure 3 is a detailed view of the filaments 36 of the heater assembly, showing a meniscus 40 of liquid aerosol-forming substrate between the heater filaments 36. It can be seen that aerosol-forming substrate contacts most of the surface of each filament so that most of the heat generated by the heater assembly passes directly into the aerosol-forming substrate.

So, in normal operation, liquid aerosol-forming substrate contacts a large portion of the surface of the heater filaments 36. However, when most of the liquid substrate in the cartridge has been used, less liquid aerosol-forming substrate will be delivered to the heater filaments. With less liquid to vaporize, less energy is taken up by the enthalpy of vaporization and more of the energy supplied to the heating filaments is directed to raising the temperature of the heating filaments. So as the heater element dries out, the rate of increase of temperature of the heater element for a given applied power will increase. The heater element may dry out because the aerosol-forming substrate in the cartridge is almost used up or because the user is taking very long or very frequent puffs and the liquid cannot be delivered to the heater filaments as fast as it is being vaporized.

In use, the heater assembly operates by resistive heating. Current is passed through the filaments 36 under the control of control electronics 16, to heat the filaments to within a desired temperature range. The mesh or array of filaments has a significantly higher electrical resistance than the electrical contacts 32 and electrical connectors 19 so that the high temperatures are localised to the filaments. In this example, the system is configured to generate heat by providing electrical current to the heater assembly in response to a user puff. In another embodiment the system may be configured to generate heat continuously while the device is in an “on” state. Different materials for the filaments may be suitable for different systems. For example, in a continuously heated system, Ni-Cr filaments are suitable as they have a relatively low specific heat capacity and are compatible with low current heating. In a puff actuated system, in which heat is generated in short bursts using high current pulses, stainless steel filaments, having a high specific heat capacity may be more suitable.

The system includes a puff sensor configured to detect when a user is drawing air through the mouthpiece portion. The puff sensor (not illustrated) is connected to the control electronics 16 and the control electronics 16 are configured to supply current to the heater assembly 30 only when it is determined that the user is puffing on the device. Any suitable air flow sensor may be used as a puff sensor, such as a microphone or pressure sensor.

In order to detect this increase in the rate of temperature change, the electric circuitry 16 is configured to measure the electrical resistance of the heater filaments. The heater filaments in this example are formed from stainless steel, and so have a positive temperature coefficient of resistance. This means that as the temperature of the heater filaments rises so does their electrical resistance.

Figure 4a is a schematic illustration of the change of resistance R of the heater during a user puff P1. The x-axis is time after initial detection of a user puff and the resulting supply of power to the heater. The y-axis is electrical resistance of the heater assembly. It can be seen that the heater assembly has an initial resistance Rbase before any heating has occurred. Rb_ase is made up of a parasitic resistance (Rp) resulting from the electrical contacts 32 and electrical connectors 19 and the contact between them, and the resistance of the heater filaments (RO). As power is applied to the heater during a user puff, the temperature of the heater filaments rises and so the electrical resistance of the heater filaments rises. As illustrated, at time t1 the resistance of the heater assembly is Rbase. At time t2 the resistance of the heater assembly is Rbase + AR.

The change in electrical resistance of the heater assembly from the initial resistance at time t1 to the resistance at time t2 is therefore AR.

In this example the parasitic resistance Rp is assumed to not change as the heater filaments heat up. This is because Rp is attributable to non-heated components, such as the electrical contacts 32 and electrical connectors 19. The value of Rp is assumed to be the same for all cartridges and a value is stored in the memory of the electric circuitry.

The relationship between the resistance of the heater filaments and their temperature is given by the following equation: where a is the temperature coefficient of electrical resistance of the heater filaments and AT is the change in temperature between an initial temperature before the application of power to the heater at time t1 , and the temperature at time t2.

In this example, the first quantity is a proportion of the baseline resistance Rbase. A proportion value is stored in the computer readable memory, and the first quantity AR_ac is determined from the product of the proportion value and the baseline resistance Rbase. In other example, it may be the first quantity AR_ac itself which is stored in the computer readable memory.

If the temperature of the heating element rises by more than a maximum temperature by time t2 such that the resistance of the heating element rises by more than the first quantity then there is considered to be an adverse condition, such as dry conditions at the heating element. In other words, if the resistance of the heating element rises to be equal or greater than an adverse event resistance limit R_ac, then there is considered to be an adverse condition.

An example of an adverse event being detected is shown in Figure 4b. Figure 4b is a schematic illustration of the change of resistance R of the heater during a user puff P2, following P1. At the start of the puff at time t3, the resistance R is higher than the baseline resistance determined prior to the first puff P1. This is because residual heat remains in the heating element from the first puff P1 . After the first puff P1 insufficient liquid remains in the capillary material 27, 28 of the cartridge 20 to be delivered to the heating element. Therefore, during the second puff P2, the temperature and hence the resistance of the heating element increases at a faster rate, and the resistance exceeds R_acat time t_ac.

When an adverse condition is determined by the aerosol-generating system, the aerosolgenerating system displays a warning to the user, for example via an LED light on the main body 11 of the aerosol-generating device. The aerosol-generating system may also or instead stop or reduce power supplied to the heating element from the power supply. The aerosol-generating system may also or instead enter a second mode of operation to confirm that an adverse condition is present in the aerosol-generating system. This second mode is described in more detail with reference to Figure 8.

The resistance of the heater R is a measured value. In particular, the resistance R is measured, and compared to the value of Rb_ase, at regular time interval throughout the each puff. Ideally the value of Rb_ase is measured before any heating takes place, in other words before first activation of the heater, and that measured value is used for all subsequent puffs. This avoids any error resulting from residual heat from previous puffs. Rb_ase may be measured only once for each cartridge and a detection system used to determine when a new cartridge is inserted, or Rbase may be measured each time the system is switched on.

Other adverse conditions besides dry heater conditions may be detected in this way. For example, if a cartridge having a damaged or incompatible heater, the electric circuitry can detect that and may be configured not to supply power to it. In the present example, the heater filaments are formed from stainless steel. If one or more heater filament breaks, the resistance of the heating element will increase. This increase in resistance will then be detected using the process described above.

Figure 5 is a schematic electric circuit diagram showing how the heating element resistance may be measured. In Figure 5, the heater 501 is connected to a battery 503 which provides a voltage V2. The heater resistance to be measured at a particular time is R. In series with the heater 501 , an additional resistor 505, with known resistance r is inserted connected to voltage V1, intermediate between ground and voltage V2. In order for microprocessor 507 to measure the resistance R of the heater 501 , the current through the heater 501 and the voltage across the heater 501 can both be determined. Then, the following well-known formula can be used to determine the resistance:

V = IR (2) In Figure 5, the voltage across the heater is V2-V1 and the current through the heater is I. Thus:

The additional resistor 505, whose resistance r is known, is used to determine the current I, again using (1) above. The current through the resistor 505 is I and the voltage across the resistor 505 is V1. Thus:

Thus, the microprocessor 507 can measure V2 and V1 , as the aerosol generating system is being used and, knowing the value of r, can determine the heater’s resistance, R at different times. The electric circuitry can control the supply of power to the heater in several different ways following an adverse condition being detected. Alternatively, or in addition, the electric circuitry may simply provide an indication to the use that an adverse condition has been detected. The system may include an LED or display or may comprise a microphone, and these components may be used to issue an alert of an adverse condition to the user.

Figure 6 is flow chart illustrating a method for detecting an adverse condition in an aerosolgenerating system. In a first step 600, the insertion of a cartridge, including the heater, into the device is detected. Then the device is powered on by the user in step 610 by the user pressing a button on the housing of device from and OFF to and ON state. The baseline electrical resistance of the heater Rbase is measured in step 610. In step 620 the user starts a session by puffing on the aerosol-generating system. The pressure sensor detects the start of a session due to the pressure drop at the pressure sensor. Power is then supplied to the heating element from the power supply. Also in step 620, the controller determines the first quantity AR_ac. The first quantity AR_ac is dependent on one or more parameters determined by the controller. For example, the first quantity AR_ac may be dependent on the power supplied to the heating element from the power supply. The first quantity AR_ac may be dependent on the pressure or flow rate measure by the pressure sensor. The first quantity AR_ac may be dependent on the number of puffs so far in the session, and/or the total elapsed time in the session, and/or the elapsed time since the start of the current puff. The first quantity AR_ac may be dependent on the ambient temperature, provided by a temperature sensor in the aerosol generating device, or provided from a remote server to which the aerosol-generating system is connected. The first quantity AR_ac may be dependent on the classification of the cartridge which is coupled to the aerosol-generating device. Methods and apparatuses for determining the classification of a cartridge are common in the field, and include but are not limited to optical sensing of an indicator on the cartridge using a sensor in the aerosolgenerating device, and measuring the resistance of the heating element of the cartridge. In step 630, the controller measures the resistance R of the heating element using the method described with respect to Figure 5. Also in step 630, the controller compares the resistance R of the heating element to the baseline resistance Rbase. If the resistance R of the heating element exceeds the baseline resistance Rb_ase by at least the first quantity AR_ac, then an adverse condition is determined. If an adverse condition is not determined, the method advances to step 640. At step 640, the controller determines whether the session is still in progress. This is determined by whether the button on the housing is still in an ON state. Alternative ways of determining whether a session is still in progress may also be based on comparing the time since the end of the last puff to a threshold time. If the session is not in progress, the method advances to 650, where the system is powered off. If the session is still in progress, the method loops back to step 620, where the first quantity AR_ac is re-determined and the resistance R of the heating element is measured.

Alternatively, if an adverse condition is determined at step 630, then the method advances to step 660. In this example, only one occurrence of the adverse condition is necessary for the method to advance to step 660. In alternative examples however, only when the adverse conditions are detected during a predetermined number of puffs, the pre-determined number stored in the computer readable memory, does the method advance to step 660.

At step 660, the controller switches from the first mode described in steps 620 to 640, to a second mode, in which the adverse condition is confirmed. At step 660, the controller determines a second quantity. In this example, the second quantity is a second resistance equal to a proportion of the baseline resistance. The controller also supplies power to the heating element. During the second mode, the power is insufficient for generating aerosol from the aerosol-forming substrate.

In step 670, the controller measures the resistance R of the heating element using the method described with respect to Figure 5. Also in step 670, the controller compares the resistance R of the heating element to the baseline resistance Rbase. If the resistance R of the heating element exceeds the baseline resistance Rb_ase by at least the second quantity, then an adverse condition is confirmed. If an adverse condition is not confirmed, the method advances to step 680. This may be indicative of a random large error in the reading of the resistance R of the heating element during step 630 for example. At step 680, the controller determines whether the session is still in progress. This is determined by whether the button on the housing is still in an ON state. If the session is not in progress, the method advances to 650, where the system is powered off. If the session is still in progress, the method loops back to step 620, and the system operates back in the first mode, where the first quantity AR_ac is re-determined and the resistance R of the heating element is measured.

In this example, only one occurrence of the adverse condition being not confirmed is necessary for the method to advance to step 680. In alternative examples however, only when the adverse conditions not confirmed for a predetermined number of puffs, the pre-determined number stored in the computer readable memory, does the method advance to step 680. In this alternative example, the method would instead loop around steps 660 and 670 until the adverse conditions are not confirmed for the predetermined number of puffs.

Alternatively, if an adverse condition is confirmed at step 670, then the method advances to step 690. In this example, only one occurrence of the adverse condition being confirmed is necessary for the method to advance to step 690. At step 690, the user is alerted to the adverse condition via an LED light being turned on. Power supply to the heating element is also stopped. In this example, the aerosol-generating system may only become operable in the first mode again once the cartridge has been replaced by a new cartridge, or once the cartridge has been refilled with aerosol-forming substrate.

In step 620, the controller determines the first quantity AR_ac, which may be dependent on a number of parameters as listed above. In alternative examples, the first quantity may be calculated by the controller based on one or more of the above parameters. In this example however, during each puff the first quantity is determined from look-up tables stored in the computer-readable memory. Figure 7a shows an example of a first look-up table. The first lookup table comprises a plurality of power profile values, each power profile value associated with a system profile value and a pressure difference. During each puff of the session, the controller selects a power profile from the first lookup table dependent on the system profile value and the instantaneous pressure difference measured by the pressure sensor. The system profile value is selected by a user and stored in the computer readable memory. In this example, the system profile value is selected by the user using an external device, such as a smartphone, connected to the aerosol-generating device. In another example, the system profile value may be selected by the user using at least one button or interface positioned on the housing of the aerosolgenerating device. Therefore, by adjusting the system profile, the user is able to control at least a part of the aerosol generation.

Figure 7b shows an example of a power profile table. This power profile table has a power profile value associated with it, and may be selected by the controller dependent on the system profile value and the pressure difference using the first look-up table. The power profile table comprises a plurality of phases, in this example 6 phases. Each phases has an associated duration. In this example, each duration is 1000 milliseconds long. Each phase also has an associated power value that is supplied to the heating element for the length of the associated duration. Once each duration is over, controller moves to the following phase of the power profile, and supplies power in accordance with the power value of the following phase. In this example, during the first phase, 4500 milliwatts of power is supplied from the power supply to the heating element. In each of the following phases 4000 milliwatts of power are supplied to the heating element.

Each power profile further comprises a plurality of resistance percentage increase (AR%) values. Each resistance percentage increase value is associated with one of each of the phases, and one of each of the power values. In each phase, the first quantity AR_ac is calculated by the controller from the product of the baseline resistance ARbase and the resistance percentage increase value AR%. The first quantity is therefore equal to a proportion of the baseline resistance. In this example, during the first phase, the resistance percentage increase value is 90%. In the second phase, the resistance percentage increase value is lower, at 85%. This is because the power supplied to the heating element is lower during the second phase compared to the first phase. Therefore the temperature, and hence the expected resistance, of the heating element will be lower during the second phase than the first phase. In the third to sixth phases, the resistance percentage increase values steadily increase to 89% in the sixth phase. This is because the length of time since the start of the puff is increasing, and so components of the aerosol-generating device surrounding the heating element increase in temperature. The heat lost from the heating element to these surrounding components is therefore reduced as the length of time since the start of the puff increases, and so the resistance of the heating element also increases.

Each power profile further comprises a plurality of maximum resistance increase (AR_max) values. Each maximum resistance increase value is associated with one of each of the phases, and serves as a maximum value for the first quantity AR_ac. If the controller calculates the first quantity from the product of the baseline resistance ARbase and the resistance percentage increase value AR% and the output value is greater than the associated maximum resistance increase value, the first quantity is instead set equal to the associated maximum resistance increase value. This implements a more accurate method for determining whether an adverse condition is present if, for example, the baseline resistance ARbase is abnormally high. In this example, plurality of maximum resistance increase (AR_max) values are set equal to 100 milliohms. The plurality of maximum resistance increase (AR_max) values may be adjusted based on the resistance of the heating element used however, so the plurality of maximum resistance increase (ARmax) values may be between 50 milliohms and 500 milliohms for example.

Figure 8 shows an graph of the first quantity varying during a session comprising two puffs, P1 and P2. During the first puff, the first quantity is represented by a first solid line 702, and reaches a first maximum value 704. During the first puff P1 , the controller is regularly determining the resistance of the heating element to determine whether an adverse condition is present. The end of the first puff P1 is determined by the controller when the pressure difference measured by the pressure sensor falls below a pre-determined threshold. After the first puff ends, the controller commences determining a scaled quantity, shown by dashed line 708. The scaled quantity 708 is dependent on the first maximum value 704 and the time elapsed since the end of the first puff P1. The time after the first puff is divided into five distinct time periods 706. During each time period 706, the maximum value is further reduced. In this example, each time period 706 is one second long. In the first time period, the maximum value is reduced by 1%. In the second time period, the maximum value is reduced by 1.5%. In the third time period, the maximum value is reduced by 2%. In the fourth time period, the maximum value is reduced by 2.5%. In the fifth time period, the maximum value is reduced by 3%. The second puff P2 is detected by the controller and the pressure sensor during the four of these time periods. The controller determines a first quantity value for the second puff as described above, and is shown in the dashed line 710. However, for a first part of the second puff, the first quantity value determined by the controller is less than the scaled quantity. Therefore, the first quantity is made equal to the scaled quantity until the first quantity value is equal to the scaled quantity. The first quantity used by the controller for determining whether an adverse condition is present is shown by the solid line 712. Once the first quantity value is equal to the scaled quantity, the first quantity is equal to the first quantity value as determined by the controller. In a session comprising more than two puffs, this scaling process repeats. The maximum value 714 of the first quantity during the second puff is used when determining the first quantity during the third puff.

Figure 9a shows the variation of pressure difference measured by the pressure sensor during a different session of four puffs. Figure 9a also shows the power supplied to the heating element during the session of four puffs. During the first two puffs, the pressure difference and the power supplied to the heating element follow similar patterns. During the third puff, the pressure difference measured by the pressure sensor is significantly greater throughout the duration of the puff. During the third puff, the power supplied to the heating element follows a similar pattern to that of the first two puffs This is indicative of the user puffing much stronger on the aerosol-generating system. During the fourth puff the pressure difference follows a similar pattern to that of the first two puffs. However in the fourth puff, the power supplied to the heating element is significantly reduced compared to the first three puffs. Figure 9b shows the variation of the resistance of the heating element measured by the controller during the same four puffs as in Figure 9a. Figure 9b also shows the variation in the adverse event resistance limit R_ac during the session. During the first two puffs, the resistance of the heating element and the adverse event resistance limit R_ac follow similar patterns. The resistance of the heating element rises throughout each of the first two puffs, the rate of increase slowing during each puff. The adverse event resistance limit R_ac determined by the controller rises as each of the first two puffs progress, as described with respect to Figure 7b, before levelling off. During the third puff, the resistance measured by the controller is lower than in the first two puffs. This is due to the stronger puffing by the user resulting in more rapid heat loss from the heating element, hence the reduced resistance. At the start of the third puff, the adverse event resistance limit R_ac determined by the controller is lower than at the start of the first and second puffs. This is because the power supplied at the start of the third puff is lower than the power supplied at the start of the first and second puffs. During the third puff, the adverse event resistance limit R_ac then rises as the third puffs progresses, as described with respect to Figure 7b. During the fourth puff, the resistance of the heating element measured by the controller is lower than in the first two puffs, but follows a similar pattern to that of the first two puffs. The resistance rises throughout the fourth puff, faster at first before slowing down. At the start of the fourth puff, the adverse event resistance limit R_ac determined by the controller is higher than at the start of the first, second and third puffs. This is because the time between the third puff and the fourth puff is smaller than the time between the first and second, or second and third puffs. Therefore, the scaling process described in Figure 8 affects the adverse event resistance limit R_ac. The adverse event resistance limit R_ac decreases at the start of the fourth puff, following the scaling of the previous maximum value of the adverse event resistance limit R_ac from the third puff. The adverse event resistance limit R_ac throughout the fourth puff is lower than the first, second and third puffs, as the power supplied to the heating element throughout the fourth puff is lower than for the first, second and third puffs.

It should be clear that the invention may be implemented as a computer program product for execution on programmable controllers within existing aerosol-generating systems. The computer program product may be provided as a downloadable piece of software or on a computer readable medium such as a compact disc.

The exemplary embodiments described above illustrate but are not limiting. In view of the above discussed exemplary embodiments, other embodiments consistent with the above exemplary embodiments will now be apparent to one of ordinary skill in the art.

Claims

1. An aerosol-generating system comprising: a heating element for heating an aerosol-forming substrate; a power supply for supplying power to the heating element; and a controller, the controller configured to: in a first mode, control the power to the heating element from the power supply; measure or determine a baseline resistance of the heating element; measure the resistance of the heating element during a session of one or more puffs; compare the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance; and determine an adverse condition when the resistance exceeds the baseline resistance by a first quantity; wherein in the first mode the controller is configured to continually adjust the first quantity during the session dependent on one or more parameters measured or determined by the controller.

2. An aerosol-generating system according to claim 1 , wherein the aerosol-generating system is configured to display a warning to a user when the controller determines an adverse condition during one or more puffs.

3. An aerosol-generating system according to claim 1 or 2, wherein the controller is configured to stop or reduce power supplied to the heating element when the controller determines an adverse condition during one or more puffs.

4. An aerosol-generating system according to any preceding claim, wherein the controller is configured to adjust the first quantity during each of the one or more puffs dependent on the power supplied to the heating element.

5. An aerosol-generating system according to any preceding claim, wherein the controller is configured to adjust the first quantity dependent on a time elapsed since an end of a preceding puff in the session.

6. An aerosol-generating system according to claim 5, wherein the controller is configured to calculate a scaled quantity following the end of each puff in the session, the scaled quantity dependent on a maximum value of the first quantity during a preceding puff in the session, and adjust the scaled quantity dependent on a time elapsed since an end of the preceding puff.

7. An aerosol-generating system according to claim 6 wherein the controller is configured to calculate or determine a first quantity value during each ensuing puff, and the controller is further configured to adjust the first quantity during each ensuing puff in the session such that the first quantity is equal to the scaled quantity until the first quantity value exceeds the scaled quantity.

8. An aerosol-generating system according to any preceding claim, wherein when the controller determines an adverse condition during one or more puffs, the controller is configured to switch from the first mode to a second mode, and wherein in the second mode the controller is configured to confirm an adverse condition when the resistance exceeds the baseline resistance by a second quantity.

9. An aerosol-generating system according to any preceding claim, wherein the aerosolgenerating system further comprises an air inlet and an air outlet; and an air flow passage extending between the air inlet and the air outlet

10. An aerosol-generating system according to claim 9, wherein the aerosol-generating system further comprises a sensor assembly in communication with the air flow passage, the sensor assembly being configured to measure a pressure or a flow rate within the airflow passage.

11. An aerosol-generating system according to claim 10, wherein the controller comprises a computer readable memory.

12. An aerosol-generating system according to claim 11 , wherein the computer readable memory stores a look-up table comprising a plurality of power profiles and a plurality of ranges of pressure or the flow rate, wherein each of the ranges of the pressure or the flow rate correspond to at least one of the power profiles, and wherein the controller is further configured in the first mode to select a power profile from the plurality of power profiles to control the supply of power to the heating element during a puff, the selection dependent on the pressure or the flow rate measured by the sensor assembly.

13. An aerosol-generating system according to claim 12 wherein each power profile comprises a plurality of power values, and each of the plurality of power values corresponding to a range of time since the start of a puff , and wherein the controller is configured in the first mode to control the supply of power to the heating element during a puff dependent on the plurality of power values and the time since the start of the puff.

14. An aerosol-generating system according to claim 13 wherein each power profile further comprises a plurality of first quantity values, wherein each of the plurality of first quantity values correspond to one of the plurality of power values, and wherein the controller is configured to adjust the first quantity dependent on a selected first quantity value from the first quantity values stored in the look-up table.

15. A method of determining an adverse condition in an aerosol-generating system, the aerosolgenerating system comprising: a heating element for heating an aerosol-forming substrate; a power supply for supplying power to the heating element; and a controller, the method comprising the steps of: in a first mode, controlling the power to the heating element from the power supply; measuring or determining a baseline resistance of the heating element; measuring the resistance of the heating element during a session of one or more puffs; comparing the resistance of the heating element to the baseline resistance or to a threshold based on the baseline resistance; determining an adverse condition when the resistance exceeds the baseline resistance by a first quantity; and continually adjusting the first quantity during the session dependent on one or more parameters measured or determined by the controller.